clicking/tapping between buffers for AudioQueue

Question

As you can see from the code, within my callback I extract out the audio data and place it into NSData data, then send that off to another class to upload that to the server. This all works, meaning the server receives and plays the audio data. HOWEVER there is a clicking or tapping noise between the buffers. I am hoping someone might show me what is causing that and how it can be fixed. I have read other related postings however they all seemed to refer to only using 1 buffer and that adding more was the fix but I am using 3 buffers and have tried adjusting that number which did not fix it

AQRecorder.mm

#include "AQRecorder.h"
RestClient * restClient;
NSData* data;


// ____________________________________________________________________________________
// Determine the size, in bytes, of a buffer necessary to represent the supplied number
// of seconds of audio data.
int AQRecorder::ComputeRecordBufferSize(const AudioStreamBasicDescription *format, float seconds)
{
    int packets, frames, bytes = 0;
    try {
        frames = (int)ceil(seconds * format->mSampleRate);

        if (format->mBytesPerFrame > 0)
            bytes = frames * format->mBytesPerFrame;
        else {
            UInt32 maxPacketSize;
            if (format->mBytesPerPacket > 0)
                maxPacketSize = format->mBytesPerPacket;    // constant packet size
            else {
                UInt32 propertySize = sizeof(maxPacketSize);
                XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_MaximumOutputPacketSize, &maxPacketSize,
                                                 &propertySize), "couldn't get queue's maximum output packet size");
            }
            if (format->mFramesPerPacket > 0)
                packets = frames / format->mFramesPerPacket;
            else
                packets = frames;   // worst-case scenario: 1 frame in a packet
            if (packets == 0)       // sanity check
                packets = 1;
            bytes = packets * maxPacketSize;
        }
    } catch (CAXException e) {
        char buf[256];
        fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf));
        return 0;
    }   
    return bytes;
}

// ____________________________________________________________________________________
// AudioQueue callback function, called when an input buffers has been filled.
void AQRecorder::MyInputBufferHandler(  void *                              inUserData,
                                        AudioQueueRef                       inAQ,
                                        AudioQueueBufferRef                 inBuffer,
                                        const AudioTimeStamp *              inStartTime,
                                        UInt32                              inNumPackets,
                                        const AudioStreamPacketDescription* inPacketDesc)
{
    AQRecorder *aqr = (AQRecorder *)inUserData;


    try {
        if (inNumPackets > 0) {
            // write packets to file
//          XThrowIfError(AudioFileWritePackets(aqr->mRecordFile, FALSE, inBuffer->mAudioDataByteSize,
//                                           inPacketDesc, aqr->mRecordPacket, &inNumPackets, inBuffer->mAudioData),
//                     "AudioFileWritePackets failed");
            aqr->mRecordPacket += inNumPackets;



//            int numBytes = inBuffer->mAudioDataByteSize;       
//            SInt8 *testBuffer = (SInt8*)inBuffer->mAudioData;
//            
//            for (int i=0; i < numBytes; i++)
//            {
//                SInt8 currentData = testBuffer[i];
//                printf("Current data in testbuffer is %d", currentData);
//                
//                NSData * temp = [NSData dataWithBytes:currentData length:sizeof(currentData)];
//            }


            data=[[NSData dataWithBytes:inBuffer->mAudioData length:inBuffer->mAudioDataByteSize]retain];

            [restClient uploadAudioData:data url:nil];

        }


        // if we're not stopping, re-enqueue the buffer so that it gets filled again
        if (aqr->IsRunning())
            XThrowIfError(AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL), "AudioQueueEnqueueBuffer failed");
    } catch (CAXException e) {
        char buf[256];
        fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf));
    }

}

AQRecorder::AQRecorder()
{
    mIsRunning = false;
    mRecordPacket = 0;

    data = [[NSData alloc]init];
    restClient = [[RestClient sharedManager]retain];
}

AQRecorder::~AQRecorder()
{
    AudioQueueDispose(mQueue, TRUE);
    AudioFileClose(mRecordFile);

    if (mFileName){
     CFRelease(mFileName);   
    }

    [restClient release];
    [data release];
}

// ____________________________________________________________________________________
// Copy a queue's encoder's magic cookie to an audio file.
void AQRecorder::CopyEncoderCookieToFile()
{
    UInt32 propertySize;
    // get the magic cookie, if any, from the converter     
    OSStatus err = AudioQueueGetPropertySize(mQueue, kAudioQueueProperty_MagicCookie, &propertySize);

    // we can get a noErr result and also a propertySize == 0
    // -- if the file format does support magic cookies, but this file doesn't have one.
    if (err == noErr && propertySize > 0) {
        Byte *magicCookie = new Byte[propertySize];
        UInt32 magicCookieSize;
        XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_MagicCookie, magicCookie, &propertySize), "get audio converter's magic cookie");
        magicCookieSize = propertySize; // the converter lies and tell us the wrong size

        // now set the magic cookie on the output file
        UInt32 willEatTheCookie = false;
        // the converter wants to give us one; will the file take it?
        err = AudioFileGetPropertyInfo(mRecordFile, kAudioFilePropertyMagicCookieData, NULL, &willEatTheCookie);
        if (err == noErr && willEatTheCookie) {
            err = AudioFileSetProperty(mRecordFile, kAudioFilePropertyMagicCookieData, magicCookieSize, magicCookie);
            XThrowIfError(err, "set audio file's magic cookie");
        }
        delete[] magicCookie;
    }
}

void AQRecorder::SetupAudioFormat(UInt32 inFormatID)
{
    memset(&mRecordFormat, 0, sizeof(mRecordFormat));

    UInt32 size = sizeof(mRecordFormat.mSampleRate);
    XThrowIfError(AudioSessionGetProperty(  kAudioSessionProperty_CurrentHardwareSampleRate,
                                        &size, 
                                        &mRecordFormat.mSampleRate), "couldn't get hardware sample rate");

    //override samplearate to 8k from device sample rate

    mRecordFormat.mSampleRate = 8000.0;

    size = sizeof(mRecordFormat.mChannelsPerFrame);
    XThrowIfError(AudioSessionGetProperty(  kAudioSessionProperty_CurrentHardwareInputNumberChannels, 
                                        &size, 
                                        &mRecordFormat.mChannelsPerFrame), "couldn't get input channel count");


//    mRecordFormat.mChannelsPerFrame = 1;

    mRecordFormat.mFormatID = inFormatID;
    if (inFormatID == kAudioFormatLinearPCM)
    {
        // if we want pcm, default to signed 16-bit little-endian
        mRecordFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
        mRecordFormat.mBitsPerChannel = 16;
        mRecordFormat.mBytesPerPacket = mRecordFormat.mBytesPerFrame = (mRecordFormat.mBitsPerChannel / 8) * mRecordFormat.mChannelsPerFrame;
        mRecordFormat.mFramesPerPacket = 1;
    }

    if (inFormatID == kAudioFormatULaw) {
        NSLog(@"is ulaw");
        mRecordFormat.mSampleRate = 8000.0;
        mRecordFormat.mFormatFlags = 0;
        mRecordFormat.mFramesPerPacket = 1;
        mRecordFormat.mChannelsPerFrame = 1;
        mRecordFormat.mBitsPerChannel = 8;
        mRecordFormat.mBytesPerPacket = 1;
        mRecordFormat.mBytesPerFrame = 1;
    }
}

NSString * GetDocumentDirectory(void)
{    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}


void AQRecorder::StartRecord(CFStringRef inRecordFile)
{
    int i, bufferByteSize;
    UInt32 size;
    CFURLRef url;

    try {       
        mFileName = CFStringCreateCopy(kCFAllocatorDefault, inRecordFile);

        // specify the recording format
        SetupAudioFormat(kAudioFormatULaw /*kAudioFormatLinearPCM*/);

        // create the queue
        XThrowIfError(AudioQueueNewInput(
                                      &mRecordFormat,
                                      MyInputBufferHandler,
                                      this /* userData */,
                                      NULL /* run loop */, NULL /* run loop mode */,
                                      0 /* flags */, &mQueue), "AudioQueueNewInput failed");

        // get the record format back from the queue's audio converter --
        // the file may require a more specific stream description than was necessary to create the encoder.
        mRecordPacket = 0;

        size = sizeof(mRecordFormat);
        XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_StreamDescription,  
                                         &mRecordFormat, &size), "couldn't get queue's format");

        NSString *basePath = GetDocumentDirectory();
        NSString *recordFile = [basePath /*NSTemporaryDirectory()*/ stringByAppendingPathComponent: (NSString*)inRecordFile];   

        url = CFURLCreateWithString(kCFAllocatorDefault, (CFStringRef)recordFile, NULL);

        // create the audio file
        XThrowIfError(AudioFileCreateWithURL(url, kAudioFileCAFType, &mRecordFormat, kAudioFileFlags_EraseFile,
                                          &mRecordFile), "AudioFileCreateWithURL failed");
        CFRelease(url);

        // copy the cookie first to give the file object as much info as we can about the data going in
        // not necessary for pcm, but required for some compressed audio
        CopyEncoderCookieToFile();


        // allocate and enqueue buffers
        bufferByteSize = ComputeRecordBufferSize(&mRecordFormat, kBufferDurationSeconds);   // enough bytes for half a second
        for (i = 0; i < kNumberRecordBuffers; ++i) {
            XThrowIfError(AudioQueueAllocateBuffer(mQueue, bufferByteSize, &mBuffers[i]),
                       "AudioQueueAllocateBuffer failed");
            XThrowIfError(AudioQueueEnqueueBuffer(mQueue, mBuffers[i], 0, NULL),
                       "AudioQueueEnqueueBuffer failed");
        }
        // start the queue
        mIsRunning = true;
        XThrowIfError(AudioQueueStart(mQueue, NULL), "AudioQueueStart failed");
    }
    catch (CAXException &e) {
        char buf[256];
        fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf));
    }
    catch (...) {
        fprintf(stderr, "An unknown error occurred\n");
    }   

}

void AQRecorder::StopRecord()
{
    // end recording
    mIsRunning = false;
//    XThrowIfError(AudioQueueReset(mQueue), "AudioQueueStop failed");  
    XThrowIfError(AudioQueueStop(mQueue, true), "AudioQueueStop failed");   
    // a codec may update its cookie at the end of an encoding session, so reapply it to the file now
    CopyEncoderCookieToFile();
    if (mFileName)
    {
        CFRelease(mFileName);
        mFileName = NULL;
    }
    AudioQueueDispose(mQueue, true);
    AudioFileClose(mRecordFile);
}

Answer 1

I changed my #define kBufferDurationSeconds from .5 to 5.0 and although the clicking is still there it is alot less noticeable.
Please if you have suggestions/answer still post as this is not a fix merely a work around thats somewhat better then before

I also tried to append data to data for a number of times prior to sending the data to the server. This also seems to have helped.